Electron tube



Patented Mar. 15, 1938 UNITED lSTATES :PATENT GFFICE ELECTRON TUBEApplication July 27, 1934, serial No. 137,135 In Germany July 31, 193310 Claims.

The invention relates to an arrangement by means of which a smallfluorescent spot can be produced on a luminous screen of a cathode raytube. To this end, and4 in accordance with the invention, the electronrays after leaving the cathode are to pass through one or severalelectrodes whose opening is large as compared with the cross section ofthe.electron ray beam,and the electrodes are to have a positivepotential applied relative to the cathode which is the higher thefarther the respective electrode is apart from the cathode. An electrodeopening is to be considered large in this connection relative to thecross section'of the beam'if the equi-potential surfaces of the eldproduced by theelectrodes are practically parallel to each other withinthe entire cross section of the ray.

The invention will be described in the following on hand of severalembodiments given by way of example and schematically represented in thedrawing in which Fig. 1 shows one embodiment of applicants invention;

Fig. 2 shows a modification of the embodiment shown in Fig. 1;

Fig. 3 shows graphically the potential distribution illustrative of thatused in connection with applicants invention; and

Figs. 4 through 9 show other embodiments and modifications of applicantsinvention.

In Fig. 1, I designates the cathode, II the lead-in for the controlgrid, which in cathode ray tubes serving for the reception of televisiontransmissions, can be used for the modulation of the brilliancy of theluminous spot. The'cathode I0 is conductinglyA connected to a disk I2,serving for rendering homogeneous the field ofthe electrodes. Thesecylindrical electrodes are designated by I3, I4, I5, and they have apositive potential applied to which increases with an lncreasingdistance from the cathode I0. In these values of the potentials as wellas in the examples of embodiments to follow, the cathode potential is lassumed to be zero. Furthermore an additional cylindrical electrode I5is provided covered at the 45 top by a mesh I1 forming the anode of thetube. A magnetic field concentrating coil is designated by I8.

The arrangement shown in Fig. 1 operates in the manner that in the axisof the cathode ray tube, the equi-potential surfaces assigned to theelectrical field produced by the electrodes I3 to I5 are practicallyparallel and at right angles to the tube axis, and that therefore thebeam of electron rays whose axis coincides with the axis of the tube,and whose cross section is small as (Cl. Z50-27.5)

compared with the opening of the electrode, consists of practicallyparallel electron rays. In the concentrating arrangement I9 the beam ofrays is rendered convergent so that on the luminous screen of the tube(not shown in Fig. 1) a small fluorescent spot is produced.

In Fig. 2 another embodiment is shown in which the parts correspondingwith those in Fig. 1 are designated by the same reference characters.Besides the electrodes I3 to I5 a further electrode i9 is provided whichcan be designated as anode of the cathode ray tube.

The functioning of the arrangement shown in Fig. 2 as regards theparallel course of the rays is the same below cathode I0 as in thearrangement according to Fig. 1. The concentrating coil I8 acts inidentical manner as described in connection with Fig. 1.

It must be expressly pointed out that the height of the electrodes I3 toI5, their relative distance and the potential differences existingtherebetween need not have the same values as those indicated in Figs. 1and 2. In particular it might be desirable to make the electrodesunequally high and/or to choose the potential differences unequallygreat, so as to compensate possible irregularities in the course of theeld, for instance in the vicinity of the cathode, and to thereby insurea substantially parallel course of the electron rays at the entranceinto'the collector arrangement I8.

In rendering the electrode distances and the potential differencesthereof unequal it can furthermore be achieved that the equi-potentialsurfaces between cathode and anode will have a very large and accuratelydefined radius of curvature. In selecting the latter equal to thedistance between anode or cathode respectively, and luminous screen, asharp fluorescent spot can also be obtained without the use of aconcentrating coil. To this end, for instance, in case of equally highelectrodes I3 to I6 and I9 respectively, the voltage at two successiveelectrodes must be higher than between the two preceding ones. Thevoltage U therefore must have a course approximately as that shown inFig. 3.

An Vembodiment containing only a single electrode in the sense of theelectrodes I3 to I5, is shown in Fig. 4.. The axialheight of electrodeI3, as Well as the voltage between the electrode and anode I9, is sodimensioned that the equi-potential lines, several thereof are shown indotted lines in Fig. 4, have such 'a curvature over the cross section ofthe beam, that they produce an accelerating and collecting action uponthe electrons. Likewise, in such an arrangement a. special concentratingcoil is therefore not required. The electrode I3 may eventually likewisehave the cathode potential applied.

In Figs. 5 and 6 the construction and mounting of the electrodes I3 toI5 is shown and also the mode of supplying the potentials thereto. InFig. 5 the electrodes consist of cylinders I3', I4' having disk-likeflanges provided thereon. These anges are drilled through and are placedover bolts 20, 2I of insulating material. The prescribed distance of theelectrodes is insured by means of spacers 22, 23. 'I'he spacers are toconsist of resistance material. The uppermost and the lowest of theelectrodes must be imagined to be connected at two sealed places throughwhich an auxiliary current is supplied. In certain conable in suchmanner that more than two sealedin places are employed. The auxiliarycurrent produces at the resistances 22, 23, etc., a voltage drop in suchmanner that the individual electrodes reach the desired potential. Thearrangement shown in Fig. 6 diners from that in Fig. 5 only by the useof disk-like electrodes I3a and I 4a in place of cylindrical electrodes.The mounting of these electrodes and the mode of supplying the voltageis carried out in the same manner as is described in connection withFig. 5.

The arrangement shown in Figs. 5 and 6 has the great advantage in thatit is not necessary to pass the voltage for each electrode through thewall of the tube, instead for the Supply of the voltage for n electrodesonly two, or at any rate considerably less than n, sealed-in places arerequired. 'I'he resistances between the individual electrodes mayeven ifresistance tubes of only a few sizes are available, within certainlimits still be regulated in that resistances as spacers are notemployed on all bolts 20, 2I or on bolts otherwise also used, but glassor porcelain tubes are provided on one or several bolts. In connectingresistance tubes of various sizes in parallel a. further stepping of thetotal resistance between two electrodes is possible. It needs not befurther explained that it is within the scope of the invention to alsoprovide between the electrodes I3, I4 small resistances of other thantube shape, for instance wire or carbon resistances.

Another embodiment which can be used in place o! the electrodes I3 to I5oi.' Figs. 1 and 2 is also shown in Fig. '7. It is namely possible toreplace the electrodes by means of helices 2l of resistance wire whichat the upper and lower end are connected by means of sealing asexplained in connection with Fig. 5. An auxiliary current is passedthrough the helical wire corresponding to the current through theresistances 22, 23, etc. (Fig. 5), and `whose voltage drop along thehelical wire produces equi-potential surfaces in the tube axis asdescribed on hand of Fig. 1. 'I'he helical wire 24 can be supported by alarger number of bolts 25, 26 of insulating material. 'I'he helicallyshaped body may likewise be composed of insulating material preferablyof glass, whereby the bolts 25, 26 can be dispensed with, and theresistance proper may itself be provided in the form of a helix on thewindings of the helix of insulating material. 'Ihe last mentioned modeof execution is shown in Fig. 'I in which the resistance wire arrangedon the helical body is designated 21.

Furthermore, the electrode can be constructed in the sense of a helixpassed by current in accordance with Fig. 7 also in such manner that aninsulating tube of large diameter preferably of porcelain is provided atthe inside witha coating of resistance material preferably of carbon inthe form of a helix.

In a further embodiment shown in Fig. 8, likewise a single electrode isto be used between cathode I0, i. e. the disk I2 connected thereto andelectrode I9 to be considered as the anode. This electrode is designatedby 28 in Fig. 8,'and may suitably consist of a cylindrical metal layer28 provided on the glass wall of the tube, for instance, by means ofevaporation in the vacuum. At the upper and low end of the electrode areinforced ring is provided also connected to the sealed-in places asdescribed on hand of Figs. 5 and 6. The auxiliary current passes throughelectrode 28 in such manner that the lower ring thereof has a positivepotential relative to the upper ring. Hence within the electrode 28, acourse of equi-potential lines is produced causing an electron ray beamof constant cross section.

On hand of Fig. 9 a further construction of electrodes is to beexplained which is of particular importance to the electrodes I3 to I5and I9 of the form represented in Figs. 1 and 2. The electrodes I3 to I5and I9 are namely intended to'be produced by evaporation of metal invacuum onto a glass or porcelain tube 29 which itself will be insertedin the cathode ray tube. 'I'he resistances 30,- 3I etc., are passed byan auxiliary current as for instance explained on hand of Fig. 5 andcauses a distribution of the voltage on the electrodes I3 to I5 and I9.

The above explanation regarding the height of the electrodes and thepotential diierences therebetween (acceleration and concentratingaction) ls also correspondingly applicable to the distance of thedisk-like electrodes I3a, Ida.I in Fig. 6 and to the size of theresistances 22, 23 in Figs. 5 and 6. Also the pitch of the helix 24 inFig. 7 and/or the specific resistance of the electrode wire or wire 21can be correspondingly selected. Finally also the thickness of the metallayer 28 in Fig. 8 along the height of the cylinder can be varied.

Besides the cathode ray tubes serving for the reception of televisiontransmission, the invention is also applicable to oscillograph tubes,furthermore to Roentgen tubes and the like.

Having thus described the invention, what we claim is:

1. An electrical lens system comprising a plurality of cylindricalannular electrodes positioned coaxially and, in register and adapted tohave linearly increasing positive potentials with respect to apredetermined point applied thereto, and a magnetic coil disposedconcentrically about the electrode adapted to have the maximum value ofthe positive potentials applied thereto.

2. An electrical lens system comprising a plurality of similarcylindrical annular electrodes disposed coaxially and in register, adissimilar electrode of greater axial length than any of the aforesaidelectrodes, said last mentioned electrode being placed coaxially and inregister with said other electrodes, and a magnetic coil disposedconcentrically about said dissimilar electrode.

3. An electrical lens system comprising a plurality of similarcylindrical annular electrodes disposed coaxially and in register, ancylindrical annular electrode of greater length than the aforesaidelectrodes and'axially aligned with said rst named electrodes, amesh-like closure element supported on the end portion oi' saidcylindrical electrode nearest said rst named series or electrodes, and amagnetic coil disposed concentrically about said cylindrical electrode.

4. An electron beam structure comprising an electron emitting cathode,an electrostatic guard disc connected thereto, a plurality of thinannular cylindrical electrodes disposed coaxially and in register withsaid cathode, and a magnetic coil surrounding the electrode positionedfurthest away from said cathode.

5. In combination an electron emitting cathode, a guard disc connectedthereto, a plurality of similar cylindrical annular electrodespositioned coaxially with said cathode and progressively spacedtherefrom, a single cylindrical annular electrode of greater length thanthe aioresaid electrodes, positioned coaxially and in register with theaforesaid electrodes, and more remote from the cathode than said nrstnamed series of electrodes, and a magnetic coil disposed concentricallyabout the last oi said electrodes.

6. In combination, an electron emitting cathode, a guard disc connectedthereto, a plurality of similar cylindrical annular electrodespositioned coaxlally and in register with said cathode, a singlecylindrical annular electrode oi greater length than the aforesaidelectrodes, positioned coaxially and in register with the aforesaidelectrodes, a magnetic coil disposed concentrically about the lastmentioned electrode, and

a series oi' electrical contact means to which suitable voltages may beapplied for subjecting said electrodes to linearly increasing potentialswith the maximum potential placed upon the last mentioned electrode, A

'1. An electrical lens system comprising a plurality of cylindricalannular electrodes positioned coaxially and in register and adapted tohave increasing potentials with respect to a predetermined point appliedthereto, the increase in potentials following a nonlinear law, and amagnetic coil disposed concentrically about the electrode adapted tohave the maximum potential applied thereto.

8. In combination, an electron emitting cathode, a guard disc connectedthereto, `a plurality of similar annular electrode elements positionedcoaxially and in register with said cathode, an elongated annularelectrode positioned coaxially and in register with the first namedelectrodes,

' a magnetic coil disposed concentrically about the last of saidelectrodes, and a series of electrical contact means to which suitablevoltages following a nonlinear law are applied to said electrodes withthe maximum voltage placed upon the last of said electrodes.

9. The tube structure claimed in claim 8 wherein said plurality ofannular electrodes com- 25 prises a series or electrically independentconducting annular areas upon the tube wall.

10. The tube structure claimed in claim 6 wherein said plurality ofannular electrodes comprises a series of electrically independent con-30 ducting annular' areas upon the tube wall.

MAX KNOLL. ERNST S0.

